U.S. patent number 4,752,810 [Application Number 06/695,495] was granted by the patent office on 1988-06-21 for cleaning apparatus for charge retentive surfaces.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Nero R. Lindblad, Fred W. Schmidlin.
United States Patent |
4,752,810 |
Schmidlin , et al. |
June 21, 1988 |
Cleaning apparatus for charge retentive surfaces
Abstract
Cleaning apparatus for charge retentive surfaces. Travelling
waves are generated by an electrode array and power source therefor
which waves both remove toner particles from a cleaning brush and
transport them to a remote location where they are collected for
disposal. The cleaning brush which removes the toner particles from
the charge retentive surface has a bias voltage applied thereto to
enhance such toner removal.
Inventors: |
Schmidlin; Fred W. (Pittsford,
NY), Lindblad; Nero R. (Ontario, NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
24793237 |
Appl.
No.: |
06/695,495 |
Filed: |
January 28, 1985 |
Current U.S.
Class: |
399/354;
15/256.52 |
Current CPC
Class: |
G03G
21/105 (20130101); G03G 21/0035 (20130101) |
Current International
Class: |
G03G
21/00 (20060101); G03G 21/10 (20060101); G03G
021/00 () |
Field of
Search: |
;355/3R,15
;15/256.51,256.52 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Braun; Fred L.
Claims
We claim:
1. Apparatus for cleaning toner particles from a charge retentive
surface, said apparatus comprising:
an endless toner particle removal member supported for movement in
a first direction such that portions thereof move into and out of
contact with said charge retentive surface; and
at least one travelling wave electrode structure stationarily
supported in contact with said particle removal member, said
electrode structure being capable of generating travelling waves
adapted to move toner particles away from said particle removal
member in a direction transverse to said first direction; and
a second travelling wave electrode structure supported out of
contact from said particle removal member, said second electrode
structure being capable of generating travelling waves for moving
toner particles in a direction substantially perpendicular to the
direction of movement caused by said at least one travelling wave
electrode structure.
2. Apparatus according to claim 1 wherein said at least one
electrode structure comprises individual electrodes which are
oriented in a direction that is substantially perpendicular to the
longitudinal axis of said particle removal member.
3. Apparatus including a charge retentive surface for forming toner
images on copy substrates, said apparatus including means for
cleaning toner particles from the charge retentive surface, said
apparatus comprising:
an endless toner particle removal member supported for movement in
a first direction such that portions thereof move into and out of
contact with said charge retentive surface; and
at least one travelling wave electrode structure stationarily
supported in contact with said particle removal member, said
electrode structure being capable of generating travelling waves
adapted to move toner particles away from said particle removal
member in a direction transverse to said direction; and
a second travelling wave electrode structure supported out of
contact from said particle removal member, said second electrode
structure being capable of generating travelling waves for moving
toner particles in a direction substantially perpendicular to the
direction of movement caused by said at least one travelling wave
electrode structure.
4. Apparatus according to claim 3 wherein said at least one
electrode structure comprises individual electrodes which are
oriented in a direction that is substantially perpendicular to the
longitudinal axis of said particle removal member.
Description
This invention relates to printing apparatus and more particularly
to cleaning apparatus for removing residual particles such as toner
from a charge retentive surface forming a part of the printing
apparatus.
In printing arts of the type contemplated, one method of forming
images uses a charge retentive surface such as a photoreceptor or
photoconductor. It comprises a photoconductive insulating material
adhered to a conductive backing which is charged uniformly. Then
the photoreceptor is exposed to a light image of an original
document to be reproduced. The latent electrostatic images, thus
formed, are rendered visible by applying any one of numerous
pigmented resins specifically designed for this purpose. In the
case of toner which forms the visible images is transferred to
plain paper. After transfer, the toner images are made to adhere to
the copy medium usually through the application of heat and
pressure by means of a roll fuser.
Although a preponderance of the toner forming the images is
transferred to the paper during transfer, some toner remains on the
photoreceptor surface, it being held thereto by relatively high
electrostatic and/or mechanical forces. It is essential for optimum
operation that the toner and debris remaining on the surface be
cleaned thoroughly therefrom.
A commercially successful mode of cleaning employed in automatic
xerography utilizes a brush with soft bristles which have suitable
triboelectric characteristics. While the bristles are soft they are
sufficiently firm to remove residual toner particles from the
xerographic plate. In addition, webs or belts of soft fibrous or
tacky materials and other cleaning systems are known.
More recent developments in the area of removing residual toner and
debris from a charge retentive surface have resulted in cleaning
structures which, in addition to relying on the physical contacting
of the surface to be acted upon also rely on electrostatic fields
established by electrically biasing one or more members of the
cleaner system.
It has been found that establishing an electrostatic field between
the charge retentive surface and the cleaning member such as a
fiber brush or a magnetic brush enhances toner attraction to the
cleaning brush surface. Such arrangements are disclosed in U.S.
Pats. Nos. 3,572,923 and 3,722,018 granted to Fisher et al on Mar.
22, 1973 and Fisher on Mar. 30, 1971, respectively. Likewise, when
an electrostatic field is established between the brush and a brush
detoning member, removal of toner from the brush is improved. The
creation of the electrostatic field between the brush and
photoreceptor is accomplished by applying a d.c. voltage to the
brush. When the fibers or granules forming the brush are
electrically conductive and a bias is applied thereto cleaning is
observed to be more efficient than if the fibers or granules are
non-conductive or insulative.
U.S. patent application Ser. No. 130,805 filed Mar. 17, 1980 now
abandoned in the name of Seanor et al and assigned to the same
assignee as this invention discloses a magnetic brush and
insulative detoning roll both of which have electrical biases
applied thereto for establishing the desired electrostatic fields
between the brush and the photoreceptor and between the brush and
detoning roll. This application was published in Brazil on Sept.
22, 1981.
The field established between the conductive brush and the
insulative photoreceptor is such that the toner on the
photoreceptor is positively charged then the aforementioned field
would be negative or less positive. In order to attract the toner
from the brush onto the detoning roll, the detoning roll is
electrically biased to the same polarity but a greater negative or
less positive potential than the brush.
A device that is structurally similar to the Seanor device is
disclosed in U.S. Pat. No. 4,116,555. However, that device has a
biased brush for removing background toner from a photoreceptor and
has two rolls for removing the background particles from the
background removal brush and returning same to the developer sump.
To that end, the U.S. Pat. No. 4,116,555 device utilizes two
detoning rolls which are biased to opposite polarities. In that
way, both positive and negative toner in the background areas can
be removed from the photoreceptor.
An improvement of the U.S. Pat. No. 4,116,555 device is disclosed
in U.S. patent application Ser. No. 517,151 filed July 25, 1983,
now U.S. Pat. No. 4,494,863 which is assigned to the same assignee
as the instant application. In the device disclosed in the
application Ser. No. 517,151 there are, as in the case of the U.S.
Pat. No. 4,116,555, provided two detoning rolls co-acting with an
electrically biased brush for removal of residual toner from a
charge-retentive surface such as a photoreceptor. However, the Ser.
No. 517,151 device unlike the U.S. Pat. No. 4,116,555 device is
utilized to, not only remove residual toner and debris from the
surface, but to separate the debris from the toner so that the
toner can be reused.
One of the very latest methods for transporting particulate
material employs travelling waves. U.S. Pat. No. 3,872,361 issued
to Masuda discloses an apparatus in which the flow of particulate
material along a defined path is controlled electrodynamically by
means of elongated electrodes curved concentrically to a path, as
axially spaced rings or interwound spirals. Each electrode is
axially spaced from its neighbors by a distance about equal to its
diameter and is connected with one terminal of a multi-phase
alternating high voltage source. Adjacent electrodes along the path
are connected with different terminals in a regular sequence,
producing a wave-like, non-uniform electric field that repels
electrically charged particles axially in wardly and tends to
propel them along the path.
U.S. Pat. No. 3,778,678 also issued to Masuda relates to a similar
device as that disclosed in the aforementioned U.S. Pat. No.
3,872,361.
U.S. Pat. No. 3,801,869 issued to Masuda discloses a booth in which
electrically charged particulate material is sprayed onto a
workpiece having an opposite charge, so that the particles are
electrostatically attracted to the workplace. All of the walls that
confront the workpiece are made of electrically insulating
material. A grid-like arrangement of parallel, spaced apart
electrodes, insulated from each other extends across the entire
area of every wall, parallel to a surface of the wall and in
intimate juxtaposition thereto. Each electrode is connected with
one terminal of an alternating haihg voltage source, every
electrode with a different terminal than each of the electrodes
laterally adjacent to it, to produce a constantly varying field
that electrodynamically repels particles from the wall. While the
primary purpose of the device disclosed is for powder painting, it
is contended therein that it can be used for electrostatic
printing.
The Masuda devices all utilize a relatively high voltage source
(i.e. 5-10 KV) operated at a relatively low frequency, i.e. 50 Hz,
for generating his travelling waves. In a confined area such as a
tube or between parallel plates, the use of high voltages is
tolerable and in the case of the U.S. Pat. No. 3,801,869 even
necessary since a high voltage is required to charge the initially
uncharged particles.
The movement of toner for use in xerographic development system is
disclosed in (Fuji Xerox's Japanese patent application No. 5666140)
filed in Japan on May 7, 1981, a copy of which is enclosed. In that
application, there is disclosed a device comprising an elongated
conduit which utilizes travelling waves for transporting toner from
a supply bottle to a toner hopper.
The movement of toner by means of travelling in a xerographic
cleaning device is disclosed in U.S. Pat. No. 4,423,950, issued in
the name of Shizuo Sagami. As disclosed therein, a brush is used to
remove toner from a charge retentive surface. The brush is disposed
within a housing but out of contact from it. The housing has an
electrode arrangement capable of creating travelling waves designed
to move toner about the inner surface of the housing so that it
does not agglomerate thereon.
The movement of toner in a xerogrpahic cleaner device is also
disclosed in U.S. patent application Ser. No. 563,729 filed Dec.
21, 1983, filed in the name of Ying-Wei Lin assigned to the same
assignee as the instant application.
Applicants' invention in contrast to the devices described above
uses a stationary toner conveyor having a linear electrode array
disposed adjacent the outer surface thereof. The electrodes forming
the array are in one embodiment of our invention co-extensive with
the longitudinal axis of the conveyor and are connected to a
relatively low voltage (i.e. 30-1000 volts) source operated at a
relatively higher frequency, for example, 1 Kc. The toner is
removed from a biased cleaning brush and transported from the brush
about the circumference thereof, movement being caused by the
travelling electrostatic waves generated by the electrode array.
The toner particles are continuously scattered off the surface of
the grid so that they bounce along making a miniature cloud of
toner which extends above the surface approximately one wavelength.
In the direction of motion, the clouds are about 1/8 to 1/4 of a
wavelength long, so the clouds are actually tall and skinny. Only
the particles closer to the surface actually collide with the
surface.
As will be appreciated more fully from a detailed description of
the invention, a stationary travelling wave electrode structure is
utilized for both detoning a biased cleaning and trasporting toner
to a collection area.
Other aspects of the present invention will become apparent as the
following description proceeds with reference to the drawings
wherein:
FIG. 1 is a schematic elevational view depicting an
electrophotographic printing machine incorporating the present
invention;
FIG. 2 is a schematic side elevational view of one embodiment of a
toner removal and transport device incorporated in the
invention;
FIG. 3 is a schematic front elevational view of the device
illustrated in FIG. 2;
FIG. 4 is a schematic side elevational view of another toner
removal and transport device;
FIG. 5 is a schematic front elevational view of the device of FIG.
4;
FIG. 6 is a schematic side elevational view of still another toner
removal and transport device;
FIG. 7 is a cross-sectional view of a toner transport device
incorporated in the device of FIG. 6;
FIG. 8 is a schematic side elevational view of yet another toner
removal and transport device; and
FIG. 9 is a schematic front elevational view of the device in FIG.
8.
Inasmuch as the art of electrophotographic printing is well known,
the various processing stations employed in the printing machine
illustrated in FIG. 1 will be described only briefly.
As shown in FIG. 1, the printing machine utilizes a photoconductive
belt 10 which consists of an electrically conductive substrate 11,
a charge generator layer 12 comprising photoconductive particles
randomly dispersed in an electrically insulating organic resin and
a charge transport layer 14 comprising a transparent electrically
inactive polycarbonate resin having dissolved therein one or more
diamines. A photoconductive belt of the foregoing type belt is
disclosed in U.S. Pat. No. 4,265,990 issued May 5, 1981 in the name
of Milan Stolka et al, the disclosure of which is incorporated
herein by reference. Belt 10 moves in the direction of arrow 16 to
advance successive portions thereof sequentially through the
various processing stations disposed about the path of movement
thereof.
Belt 10 is entrained about stripping roller 18, tension roller 20
and drive roller 22. Roller 22 is coupled to motor 24 by suitable
means such as a drive chain.
Belt 10 is maintained in tension by a pair of springs (not shown)
resiliently urging tension roller 20 against belt 10 with the
desired spring force. Both stripping roller 18 and tension roller
20 are rotatably mounted. These rollers are idlers which rotate
freely as belt 10 moves in the direction of arrow 16.
With continued reference to FIG. 1, initially a portion of belt 10
passes through charging station A. At charging station A, a corona
device, indicated generally by the reference numeral 25, charge
layer 14 of belt 10 to a relatively high, substantially uniform
negative potential. A suitable corona generating device for
negatively charging the photoreceptor belt 10 comprises a
conductive shield 26 and corona wire 27 the latter of which is
coated with an electrically insulating layer 28 having a thickness
which precludes a net d.c. corona current when an a.c. voltage is
applied to the corona wire. Application of a suitable d.c. bias on
the conductive shield 26 will result in suitable charge being
applied to the photoreceptor belt as it is advanced through
exposure station B. At exposure station B, an original document 30
is positioned face down upon a transparent platen 32. The light
rays reflected from original document 30 form images which are
transmitted through lens 36. The light images are projected onto
the charged portion of the photoreceptor belt to selectively
dissipate the charge thereon. This records an electrostatic latent
image on the belt which corresponds to the informational area
contained within original document 30.
Thereafter, belt 10 advances the electrostatic latent image to
development station C. At development station C, a magnetic brush
developer roller 38 advances a developer mix (i.e. toner and
carrier granules) into contact with the electrostatic latent image.
The latent image attracts the toner particles from the carrier
granules thereby forming toner powder images on the photoreceptor
belt.
Belt 10 then advances the toner powder image to transfer station D.
At transfer station D, a sheet of support material 40 is moved into
contact with the toner powder images. The sheet of support material
is advanced to transfer station D by a sheet feeding apparatus 42.
Preferably, sheet feeding apparatus 42 includes a feed roll 44
contacting the upper sheet from stack 46 into chute 48. Chute 48
directs the advancing sheet of support material into contact with
the belt 10 in a timed sequence so that the toner powder image
developed thereon contacts the advancing sheet of support material
at transfer station D.
Transfer station D includes a corona generating device 50 which
sprays ions of a suitable polarity onto the backside of sheet 40 so
that the toner powder images are attracted from photoconductive
belt 10 to sheet 40. After transfer, the sheet continues to move in
the direction of arrow 52 onto a conveyor (not shown) which
advances the sheet to fusing station E.
Fusing station E includes a fuser assembly, indicated generally by
the reference numeral 54, which permanently affixes the transferred
toner powder images to sheet 40. Preferably, fuser assembly 54
includes a heated fuser roller 56 adapted to be pressure engaged
with a back-up roller 58 with the toner powder images contacting
fuser roller 56. In this manner, the toner powder image is
permanently affixed to sheet 40. After fusing, chute 60 guides the
advancing sheet 40 to catch tray 62 for removal from the printing
machine by the operator.
A preclean dicorotron 63 is provided for exposing the residual
toner and contaminants to positive charges thereon so that a
suitably biased cleaning roller, to be discussed hereinafter, will
be more effective in removing them.
At a cleaning station F, residual particles such as toner and
contaminants or debris such as paper fibers are removed from the
photoreceptor surface by means of a brush (i.e. magnetic or fiber)
64 which is suitably biased by means of a power source 65 and which
is rotated in the direction of the arrow 66 via motor 67. While the
power source 65 is depicted as being negative for attracting
positively charged toner from the photoreceptor 10, it may comprise
a positive potential for attracting negatively charged toner. A
stationary electrode grid structure 68 (FIG. 2) serves to both
detone the brush 64 and transport the toner removed therefrom to a
collection receptacle 70 adjacent one end of the grid structure 68.
A suitable magnetic d.c. bias is applied to the grid 68 by means of
a power source 69 in order to cause the toner particles to transfer
from the brush 64 to the grid 68. The grid structure 68 is
preferably constructed in the manner described in U.S. patent
application Ser. No. 614,499 filed May 29, 1984, now U.S. Pat. No.
4,647,179, assigned to the same assignee as the instant
application. The grid structure comprises a grid array comprising
electrodes 71, the longitudinal axes of which extend from left to
right (as viewed in FIG. 2 and are disposed in a side-by-side
orientation. With the voltage source described in the
aforementioned application applied to the electrodes, a travelling
wave pattern is developed which causes toner to travel
perpendicular to the electrodes 71. In the embodiment of the
invention depicted in FIGS. 2 and 3 the brush has a generally
cylindrical shape while the grid structure has a generally planar
shape.
The embodiment of the invention disclosed in FIGS. 4 and 5 comprise
a biased brush 64 and a grid structure 68 which are identical to
the corresponding members of the embodiment of FIGS. 2 and 3. A
second electrode structure 72 comprises electrodes 74 which extend
in the direction of the longitudinal axis of the brush as viewed in
FIG. 5.
Another embodiment as illustrated in FIGS. 6 and 7 comprises a
cleaning brush 64 partially surrounded by a grid structure 80
having electrodes 82 (FIG. 7) which are positioned about the inner
circumference of an acute-shaped base portion 84 on which the
electrodes are mounted. The electrodes are disposed such that they
are perpendicualr to the longitudinal axis of the brush. The grid
structure also comprises a funnel-shaped portion 86 having
continuous electrodes 88 mounted about the inner curcumference
thereof. Toner is moved from the funnel-shaped portions 86 to a
cylindrical transport tube 92 having electrodes 94 disposed about
the inner surface thereof.
Depicted in FIGS. 8 and 9 is yet another embodiment of the
invention which comprises a brush structure 96 and a grid structure
98. The grid structure 98 has a generally cylindrically-shaped
portion 100 formed integrally with a trough 102. Electrodes 104
provided in the surface of the portion 100 are spirally oriented as
shown in FIG. 9 in order to establish a travelling wave pattern
which moves the toner removed from the brush generally along the
longitudinal axis and angularly of the brush such that it
ultimately moves into the trough 102. After the toner reaches the
trough it is moved longitudinally toward one end of the trough. As
will be appreciated in this embodiment the portion 100 and the
trough share the same electrodes whereas in the other embodiments
their counterparts have separate electrodes.
In view of the foregoing description it should now be apparent that
the cleaning apparatus disclosed utilizes travelling waves to both
remove toner from a cleaning brush and carry the toner away to a
remote point. It does so effectively with the use of a minimum
number of moving parts thereby providing a device which is less
complicated in construction.
* * * * *